An integrated permeable reactive barrier and photobioreactor approach for simultaneous removal of nitrate, phosphate...

In this study, simultaneous removal of nitrate (NO₃^-), phosphate (PO₄^3-) and hexavalent chromium (Cr(VI)) from wastewater was investigated using a novel integrated filtration unit consisting of adsorbent based permeable reactive barrier (AB-PRB) and biosorption based photobioreactor (BSB-PBR). AB-PRB was comprising a mixture of low-cost adsorbents in an optimum proportion, whereas BSB-PBR carried C. vulgaris microalgae cultivated in controlled environment. The batch analysis for AB-PRB showed maximum removal efficiency of 95.7% and 98.0% for NO₃^- and PO₄^3-, at pH-6, whereas 84.0% for Cr(VI) at pH-4. However, continuous flow study showed decreasing trend in removal efficiency of NO₃^-, PO₄^3- and Cr(VI) with increasing flow rate from 10 ml min^-1 to 30 ml min^-1. Further, in BSB-PBR, maximum removal of 98.2% was achieved for Cr(VI) of 1.0 mg L^-1 initial concentration at 3.3 days of hydraulic retention time (HRT). This study provides a novel integrated remediation approach for efficient removal of unlike contaminants.